arm64: rockchip: Add driver for the io domain

[manu]

Summary

This driver configure the registers in the GRF according to the value
of the regulators for the platform.
Some IP can run with either 3.0V or 1.8V, if we don't configure them
correctly according to the external voltage used they will not work.
It's only done at boot time for now and might be needed at runtime for IP like sdmmc.

Test Plan

Tested on RK3399

[mmel]

Tested on AIO-3288.